In one known process, the covering is laid by its outer side onto a preliminary mold, which is negative to the thermoforming mold, the joining seams subsequently being sealed by adhesion with an airtight film; thereafter the covering is turned inside out, introduced by its outer side into the thermoforming mold and foam-backed.
This process is intended in particular for the production of relatively sharp-edged foam-backed articles, which are provided with a joining seam at least along a part of their edges. In this process, the covering is laid by its outside side onto the preliminary mold in such a way that it comes to rest with a joining seam on an edge of the preliminary mold. The covering which is used in this known process has a lamination. In particular when using leather as covering material, the flame lamination of the covering produces a relatively large amount of waste. A deficient flame lamination of the covering results in its distortion and the formation of folds, which is likewise undesirable. For sealing of the joining seams, in this process an airtight film in the form of a strip is used, which is adhesively affixed along the joining seam onto the two joined covering parts, on the inside of the covering parts. This adhesive affixing of a strip-shaped airtight film requires precise, time-consuming work in order to avoid a deficient seal of the joining seams. A deficient seal of the joining seams results in the foam-producing reaction mixture being able to penetrate the seams during the foam-backing operation. In addition, a deficient seal of the joining seams can also result in an undesirable formation of folds.
A further shortcoming of the known process is that the strip-shaped film adhesively fixed on the laminated covering parts forms a material deposition in the region of the joining seams, on account of which the seam and corner shaping of the cover which is turned inside out after sealing, and of the foam-backed article, leaves something to be desired.